1. Field of the Disclosure
The present disclosure relates to a sensor package used for detecting pressure in automobiles, industrial machines, and so forth.
2. Description of the Related Art
A temperature sensor-integrated pressure sensor device described in Japanese Patent No. 3870918 includes a pressure sensor element, a lead frame electrically connected to this pressure sensor element, a connector pin electrically connected to this lead frame, and a pressure introduction hole through which a medium the pressure of which is to be measured is introduced. The pressure sensor element and the lead frame are enclosed by mold resin.
A semiconductor pressure sensor device described in Japanese Patent No. 3890739 includes a semiconductor pressure sensor chip, a resin package into which a conductive portion is insert molded, a first protective member, and a second protective member. The semiconductor pressure sensor chip is electrically connected to the conductive portion by a bonding wire. The first protective member is formed of a resin or rubber material having a comparatively high Young's modulus. At least the conductive portion, a region around the conductive portion, and a mount portion for mounting the semiconductor pressure sensor chip on the resin package is covered with the first protective member with a sensing portion of the semiconductor pressure sensor chip exposed. The second protective member is a gel or gel-like substance having a comparatively low Young's modulus and covers the sensing portion of the semiconductor pressure sensor chip and the first protective member. The bonding wire is covered with the first protective member and the second protective member.
In the pressure sensor device according to Japanese Patent No. 3870918 or Japanese Patent No. 3890739, the lead frame or the conductive portion is covered with resin. With such a structure, when contact between the lead frame or the conductive portion and the resin is not sufficiently tight, a small amount of air may remain in a gap or at an interface between the lead frame or the conductive portion and the resin while the resin is formed. Such residual air may leak as air bubbles through the gap or the interface due to a variation in pressure during detection. This may degrade accuracy of pressure detection. Furthermore, the gap between the lead frame or the conductive portion and the resin may become an air leakage path from the outside to the inside of the pressure sensor device. This degrades the accuracy of pressure detection.
In order address this, for the pressure sensor device described in Japanese Patent No. 3890739, the following structure is proposed: resin that covers the lead frame or the conductive portion has a high Young's modulus, thereby reducing the likelihood of air remaining in the gap or the interface between the lead frame or the conductive portion and the resin.
However, in the case where the resin that covers the lead frame or the conductive portion is in contact with a pressure sensor that detects pressure, when the temperature of the resin varies due to a variation in temperature of a region around a device or a variation in temperature of the lead frame, accuracy of temperature characteristics of the pressure sensor may be degraded because the pressure sensor in contact with the resin is also affected by a surrounding environment. Furthermore, in many cases a resin having a high Young's modulus has high stress while hardening. In order to suppress a variation in output of the pressure sensor due to such stress, it is preferable that a material having low stress while hardening be selected. Thus, selectable materials are limited, and accordingly, reduction of cost is difficult.
Furthermore, in the case where the sensor that senses the pressure and the lead frame or the conductive portion are integrated with each other with common resin which is part of either or both of a pressure chamber and the pressure introduction hole as is the case with the pressure sensor device according to Japanese Patent No. 3870918 or 3890739, it is required that the entirety of the pressure sensor device be attached to a calibration device for calibrating the pressure sensor. Thus, it is required that a large and complex calibration device be prepared. Accordingly, a large capital investment is required.
Furthermore, in the case where an integrated circuit (IC) board that includes a computation unit and the like that perform computation in accordance with a result of detection performed by the pressure sensor, it is required that the IC board and an element and the like connected to the IC board be covered by a highly insulative resin so as to prevent electrostatic damage. Here, when the pressure sensor is connected to the IC board through the bonding wire, the resin that covers the IC board is required to be soft so that the resin does not obstruct operation of the pressure sensor. In contrast, as described above, from the viewpoint of prevention of remaining of the air, it is preferable that the resin that covers the lead frame or the conductive portion be hard. Thus, required characteristics are different between the resin that covers the lead frame or the conductive portion and the resin that covers the IC board. Accordingly, it is required that the lead frame or the conductive portion and the IC board be disposed in respective different spaces and covered by different types of resin. This leads to a problem in that a routing pattern of the lead frame or the conductive portion and the structure around the routing pattern become complex.
These and other drawbacks exist.